The use of chains of pre-opened bags to form packages is well known. Such chains of bags are disclosed and claimed in U.S. Pat. No. 3,254,828 entitled FLEXIBLE CONTAINER STRIPS (the Autobag patent). A commercial version of a machine described and claimed in U.S. Pat. No. 3,815,318 entitled PACKAGING APPARATUS, and in other patents deriving from the application that resulted in this patent (the H-100 patents), has been sold commercially by Automated Packaging Systems, Inc. under the designation H-100. A machine described in U.S. Pat. No. 4,899,520 entitled PACKAGING APPARATUS AND METHOD includes an ability to use two chains of interconnected bags while packaging and has been sold commercially by Automated Packaging under the designation H-200.
With the machines of the H-100 and H-200 patents loaded, bags are sealed at sealing stations each through contact with a heater bar which melts a portion of the plastic. During the sealing operation, the weight of a bag's contents and bag separation forces are isolated from the seal by spring-biased grippers which are moved into bag engagement by a clamping sub-assembly that concurrently brings the loaded bag into contact with the heater bar. All of these moving parts can be interfered with by a product that is only partially loaded or a foreign object thereby causing jams which can damage the machine and/or the product or can cause an improper seal which creates an unacceptable package.